During the lifetime of a patient, it may be necessary to perform a joint replacement procedure or arthroplasty on the patient as a result of, for example, disease or trauma. One such type of joint replacement procedure is a hip replacement procedure in which a diseased and/or damaged hip joint is replaced with a prosthetic hip joint. A typical hip replacement procedure utilizes a prosthesis that generally includes a femoral stem component, a proximal body component, and a neck segment. The femoral stem is implanted in a prepared medullary canal of the patient's femur.
During performance of such a hip replacement procedure, the surgeon must evaluate the size and condition of the patient's bones (e.g. the patient's femur) in order to determine the proper type and configuration of each of the various types of prosthetic components that are to be implanted. One or more provisional components are temporarily fixed to a bone prior to permanent fixation of the prosthetic joint. The provisional components are intended to mimic certain aspects of the permanent prosthetic joint in order for a surgeon to validate measurements and to test several different possible component sizes and shapes. Hence, provisional components are aptly known as “trials”, and the procedure is known as “trialing.”
Currently, in a majority of revision total hip arthroplasties, the bone has little or no supportive metaphysis or diaphyseal areas. This makes it difficult for surgeons to reproduce the proper anatomy. To do this, the surgeon may use a distally fixed implant. This facilitates trialing from the distal femoral cortex and subsequent proximal anatomy. Many trials are used in surgery having one basic anterior/posterior proximal anatomical body with altering characteristics (i.e., stem lengths, bow, offsets, neck lengths, neck anteversion). Each instance requires a single monolithic trial that duplicates the implant, which is therein made from casting substrate. Some trialing techniques utilize the broach as the stem and then attach a proximal trial onto the broach.
Other techniques require that the broach be removed from the medullary canal to allow the use of a trial having a stem portion, a head and a neck. For example, some have disclosed a system including a group of variously sized trial neck/body portions and a group of differing length trial stem portions which are mixed and matched to create a suitable trial. The trials are held together using a ball and spring detent system. Such ball and spring systems do not create a tight, wiggle-free connection. Because the trial pieces are not held tightly together, there can be errors in the use of the actual implant.
Because many variations in sizes and shapes of trials are required to be available to the surgeon, it is necessary to maintain a large inventory of trials. Such a large inventory is costly, occupies valuable operating room space, and is difficult to manage. If the trial is a singular piece, then there must be upwards of 50 full trials. These full trials take up large amounts of space in instrument sets.
In some modular trials, the different parts of the trial are assembled using threads. However, this makes connection and disconnection lengthy and cumbersome. In other modular trial designs, the different parts are held together by nothing more than a ball plunger of balseal. These features are not suitable for a solid, wiggle-free connection which resists tensile forces as well as rotational ones. Others use the reamer as the trial stem. However, not all distal reamers are suitable for working as trials.